Effects Of Submerged Aeration Systems On Water Quality And Phytoplankton Community Structure In Aquaculture Ponds

Pnod farming , as a traditional pond culture model ,which was widely used in shrimp ,crab and fish farming , was usually equipped with aeration system fo maintain the water quality and promote the growth of culture ogganisms.And there are many aeration mode ,such as Waterwheel-type, Inflatable.Submerged-aeration systems technology is a new aeration technology,which is the major reform way of water aeration .Water quality and the community structure of phytoplankton were examined in shrimp and Portunus trituberculatus ponds with different aeration system in our survey.And we used statistical software PRIMER software ,which contain the fuction of cluster analysis, multidimensional scaling order (No-metric MDS), principal component analysis (PCA), Biological - Environmental correlation analysis (RELATE), and biological - Environmental matching analysis (BIO-ENV) ,to found the submerged-aeration systems effect on the water quality and plankton community , as well as the relathionship between environmental factors and plankton community structure. The main results are summarized as follows:1. Water quality and the community structure of phytoplankton were examined in three adjacent Portunus trituberculatus ponds with different aeration system during a three-month period from August to October 2008 in Sanmen bay, Ningbo. A total of 5 divisions comprised of 16 species of phytoplankton were identified. The abundances of the phytoplankton total densities were maintained relatively mean 274.3×10⁵indL^-1 to 5034.3×10⁵indL^-1, and with species such as Oocystis, Eudoina, Phormidium, Chroococcus, Cyclotella, Nitzschia dominating the pond. The abundances of the zooplankton varied from 1533 to 12005.7 indL-1,and with species such as Tintinnidium, Epistylis, Cyclopidae, Brachionus urceus dominating the pond.The fluctuations of the densities of cyanophytes and rotifers were the main changes of phytoplankton and zooplankton. The 1# pond ,which has bottom's oxygenation device, the dominated phytoplankton species was Oocystis ,and while the community structure of this pond was also stable . And the dissolved oxygen concentration was relatively high,while the ammonia and nitrite concentration were lower than other ponds; the dissolved oxygen concentration of 3# pond was also at a high level since the exisitence of E. prolifera , but after the death of E. prolifera ,the Phormidium increased rapidly , broke out the bloom and the pond water was deteriorated; the 2# pond was always dominated by cyanophytes,and lowest the dissolved oxygen concentration, highest ammonia and nitrite concentration, and the water quality was poorer.The production of Portunus was closely related to the pond plankton community structure.2. Water quality and the community structure of phytoplankton were examined in two adjacent shrimp (Portunus trituberculatus) ponds with different aeration system during a three-month period from June to September 2009 in Sanmen bay, Ningbo. Results showed that the water quality of the pond with submerged aeration systems was better than that of the control pond,like that dissolved oxygen concentration of the aerated pond was maintained at 5mg / L in the breeding cycle while the control pond was maintained at 4mg / L. And the ammonia concentration at the aerated pond was much lower than that at the control pond in the later farming phases. In addition, phytoplankton concentration at the pond with submerged aeration systems is much higher than that at the control pond, particularly green algae concentration. And the MDS analysis revealed significant differences between the two ponds, and aerated pond phytoplankton community structure was stable in the later phase of culture, contrast to the volatile and unstable phytoplankton community structure of control pond. The dissimilarity of two ponds was as high as 84.44 percent, and the dominant species of submerged aeration systems pond were Oocystis, while the dominant sepecies in control ponds were some species of diatom and cyanobacteria. BIO-ENV analysis showed that there were most relevant between dissolved oxygen variable and the phytoplankton abundance. Compared to the ordinary type of aeration systems, the investigation results revealed that the function of submerged aeration systems was not only to improve the DO concentration of the aquaculture ponds, but also to stabilize community structure of the algae in the farming pond during the shrimp culture.3. Water quality, plankton species and biomass were examined in three adjacent shrimp ponds equipped with submerged-aeration systems during a three-month period, from June to August 2009 in Ningbo, China. A total of 56 species of plankton were identified, comprising 31 species of phytoplankton (13Chlorophyceans,7 Cyanobacteria , 8 Diatoms, 2 Dinoflagellates and 1 Euglenophyta) and 25 species of zooplankton (2 Copepods, 1 Cladocera, 13 Rotifers, 8 Protozoas and 2 larvae ). Three successional series stages of planktonic community were identified according to community structure.tage I (from 12 June to 29 June) was the initial period of series when shrimp juveniles were introducted into the pond, with the characteristics of high abundance of chlorophyceans and less protozoa. In stage II , the phytoplankton species richness decreased and zooplankton richness gradually increased with culture time. The concentration of nutrients was at its peak in stage III , while many phytoplankton were disappeared and the protozoa were dominant.The Margalef index of phytoplankton showed a decline trend with the progress of successional series. The dominance plots displayed significant differences among three stages with a higher diversity in stage I than in stage II and III. It was concluded the plankton are the excellent indicator of environmental conditions and water quality conditions.4. Water quality, plankton species and biomass were examined in three adjacent shrimp ponds equipped with submerged-aeration systems from May to September 2009 in Cixi freshwater shrimp ponds. A total of 69 species of plankton were identified, comprising 41 species of phytoplankton and 28species of zooplankton during sampling. The density of Cyanobacteria , which accounted for most of the phytoplankton concentration, were similar to it showing a sine wave trend . The whole succession process of the phytoplankton was from the blue and green algae as the dominant species in the pond water to of cyanobacteria as the dominant species change. And green algae in the phytoplankton community structure occupied a certain position in the early days , as the dominant species of algae Scenedesmus and oocysts.Throughout the sampling period , the rotifers and copepods were the dominant species in the zooplankton community ,while protozoa accounted for a minority abundance.And the dominant species of rotifers were Brachionus angularis and Proales..Tthey occupied the dominance place in turn in zooplankton in the sampling period. MDS analysis revealed that there are greater difference in the initial sampling of the plankton community,while in the later breeding stages ,three ponds had the same phytoplankton community structure.